Mixed Martial Arts Group's (MMA) stock skyrocketed over 100% in premarket trading on Tuesday after announcing that Donald Trump Jr. would join as a strategic advisor. The combat sports company, trading under the ticker MMA, saw its stock surge from 85 cents to above $1 for the first time since August. MMA stock is now priced around $1.76. www,barchart.com Trump Jr. will provide strategic counsel to enhance global recognition and accelerate the commercialization of MMA’s platforms, technology, and trainin ...